文档介绍：R – Pd – X + R ′– M
(M = Si, etc.)
Overview of Other
Palladium-Catalyzed Cross-Coupling
Protocols
TAMEJIRO HIYAMA and EIJI SHIRAKAWA
'
A. INTRODUCTION
In this section is reviewed the cross-coupling reaction pounds con-
taining a main group metal such as Si, Ge, Cd, In, Hg, Pb, or Bi, not covered in Sects.
–. The carbon–metal bond of pounds, although less polarized than
those of anometallics covered in preceding sections, has sufficient but not immod-
erate nucleophilicity to react with palladium(II) complexes. This character leads to
chemoselective cross-coupling reactions. pounds have a weakly polar-
ized C—Si bond and thus often need activation by a Lewis base to couple with elec-
trophiles. pounds having electron-withdrawing ligands sometimes act
as an electrophile to react with pounds, giving cross-
coupled products.
B. POUNDS[1]–[4]
. Alkenylsilane
anosilanes (R—SiMe3) are weak nucleophiles among anometallics de-
scribed in this section and generally do not undergo a desilylative coupling reaction with
aryl halides in the presence of a palladium catalyst except for the following examples.
Hallberg and Westerlund[5] reported that although trimethyl(vinyl)silane could transmeta-
late with an arylpalladium(II) complex to afford coupled products, aryl-substituted
alkenylsilanes formed through the Heck type reaction also panied (Scheme 1). On
the other hand, Kikukawa and co-workers[6]–[8] found that the reaction of trimethyl(␣- or
-styryl)silanes with arenediazonium tetrafluoroborates gave a regioisomeric mixture of
coupling products. The catalytic cycle of the reaction is considered to involve carbopalla-
dation toward the C—C double bond of an alkenylsilane by an arylpalladium intermedi-
ate followed by tetrafluoroborate-assisted elimination of the silyl group and palladium(0)
(Scheme 2).
Handbook anopalladium Chemistry anic Synthesis, Edited by Ei-ichi Negishi
ISBN 0-471-31506-0 © 2002 John Wiley & Sons,